Image forming apparatus

ABSTRACT

The image forming apparatus in this disclosure includes a main body, a plate-shaped frame member, a perforated portion, a sound generating source, an external cover member, and a space forming portion. The plate-shaped frame member configures a part or the whole of the side surface of the main body. The perforated portion has a plurality of holes and is formed in the frame member. The sound generating source is an inner portion of the main body and is disposed at a position corresponding to the perforated portion. The external cover member is disposed at and separated by a predetermined distance from the frame member on an outer side of the frame member. The space forming portion forms a space between the perforated portion and the external cover member that is tightly enclosed except for the perforated portion.

This application is based on and claims the benefit of priority fromJapanese Patent Application No. 2010-287071, filed on 24 Dec. 2010, thecontent of which is incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to an image forming apparatus.

2. Related Art

Recently, problems caused by an increase in sound with operating ofmachines due to an enhanced operating speed of the machines haveoccurred in relation to a so-called electrographic type of image formingapparatus used in offices and the like. As a result, for example,various proposals have been made to suppress emission to the outside ofsound generated in an internal portion of an apparatus, such as fanrotational sound, gear driving sound, or the like.

For example, a configuration has been disclosed as a related techniquein which emission of fan rotational sound to the outside is suppressedby increasing a suppressible frequency by disposing a silencingapparatus on an outer side of the fan. The silencing apparatus includestwo plate members that have a plurality of holes adapted for silencing.

SUMMARY OF THE DISCLOSURE

However, the silencing apparatus in the related technique is a separatecomponent to the frame or the external cover of the apparatus. As aresult, increase in the product size or the manufacturing cost mayresult.

The present disclosure has the object of providing an image formingapparatus having a configuration in which emission of sound produced inthe apparatus internal portion is suppressed.

The image forming apparatus in this disclosure includes a main body, aplate-shaped frame member, a perforated portion, a sound generatingsource, an external cover member, and a space forming portion. Theplate-shaped frame member configures a part or the whole of the sidesurface of the main body. The perforated portion has a plurality ofholes and is formed in the frame member. The sound generating source isan inner portion of the main body and is disposed at a positioncorresponding to the perforated portion. The external cover member isdisposed at and separated by a predetermined distance from the framemember on an outer side of the frame member. The space forming portionforms a space between the perforated portion and the external covermember that is tightly enclosed except for the perforated portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of an image forming apparatusaccording to an embodiment of the present disclosure.

FIG. 2 is a perspective view seen from the inner side of the main bodyframe in the image forming apparatus according to an embodiment of thepresent disclosure.

FIG. 3 is a perspective view seen from the outer side of the main bodyframe in the image forming apparatus according to an embodiment of thepresent disclosure.

FIG. 4 is a perspective view of the main body frame mounting a driveunit and a right cover in the image forming apparatus according to anembodiment of the present disclosure.

FIG. 5 is a perspective view seen from the inner side of the drive unitin the image forming apparatus according to an embodiment of the presentdisclosure.

FIG. 6 is a perspective view seen from the outer side of the drive unitin the image forming apparatus according to an embodiment of the presentinvention.

FIG. 7 is a perspective view of the right cover in the image formingapparatus according to an embodiment of the present disclosure.

FIG. 8 is a perspective view of the shape of a space formed between amain body frame and a right cover in the image forming apparatusaccording to an embodiment of the present disclosure.

FIG. 9 is a perspective view illustrating the positional relationship ofthe drive unit and the right cover in the image forming apparatusaccording to an embodiment of the present disclosure.

FIG. 10 is a perspective view describing the shape of a space formedbetween an attachment plate and a right cover in the image formingapparatus according to an embodiment of the present disclosure.

FIG. 11 is a table describing the interval between the main body frameand the right cover, and the aperture diameter and hole interval in eachembodiment in relation to the image forming apparatus according to anembodiment of the present disclosure.

FIG. 12 is a table describing the relationship between the soundpressure level and the sound frequency in the embodiments andcomparative examples in the image forming apparatus according to anembodiment of the present disclosure.

FIG. 13 is a graph describing the relationship between the soundpressure level and the sound frequency in the embodiments andcomparative examples in the image forming apparatus according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

A monochrome printer 1 will be described below making reference to FIG.1 to FIG. 10 as an example of the image forming apparatus according toan embodiment of the present disclosure. In the following description,the surface at the front of FIG. 1 is used as the front side of themonochromatic printer 1.

As illustrated in FIG. 1, the monochromatic printer 1 includes asubstantially rectangular main body 2 and an external cover 3 thatcovers the external periphery of the main body 2.

A plate-shaped main body frame 4 that acts as a frame member isconfigured in an upright orientation on an inner right side of the mainbody 2 to be substantially parallel to the right surface of the mainbody 2. The main body frame 4 is configured as a portion of the rightside surface in the main body 2. FIG. 2 is a perspective view of themain body frame 4 seen from the inner side of the main body 2, and theright side in FIG. 2 is the front side of the main body 2. In contrast,FIG. 3 is a perspective view of the main body frame 4 seen from theouter side of the main body 2, and the left side in FIG. 3 is the frontside of the main body 2.

The main body frame 4 is formed by a sheet metal member. As illustratedin FIG. 2 and FIG. 3, a bulging portion 5 is provided on the main bodyframe 4 to project from the central longitudinal portion toward the rearend portion in an inward orientation in the main body 2. The bulgingportion 5 is configured to include an upper portion 6 provided from acentral portion in a longitudinal direction of the main body frame 4 toa predetermined rear position and a lower portion 7 formed below theupper portion 6 and positioned further towards a rear outer edge. Thebulging portion 5 is formed in the shape of a letter “L” when viewedfrom the side.

A motor mounting portion 11 including a circular insertion hole 8, andengaging holes 10, 10 provided above and below the insertion hole 8 isprovided on the upper portion 6 of the bulging portion 5. A motor 12 ismounted from the outer side onto the motor mounting portion 11 (refer toFIG. 4).

A perforated portion 14 is formed as a horizontally long rectangle onthe lower portion 7 of the bulging portion 5 from a predeterminedforward position of the lower portion 7 towards the rear end portion. Agear train 16 configured to include a plurality of intermeshing gears 15is disposed on an inner side of the perforated portion 14 in a state inwhich the position in the longitudinal direction is slightly staggeredforward with respect to the perforated portion 14. In other words, thefront end of the gear train 16 in relation to the longitudinal directionis disposed more in a forward orientation than the front end of theperforated portion 14, and the rear end is disposed more in a forwardorientation than the rear end of the perforated portion 14. The geartrain 16 is omitted from the figures other than FIG. 4.

The perforated portion 14 includes a plurality of holes 13. The aperturediameter and the hole interval (refer to the arrow a in FIG. 2) of theplurality of holes 13 is set in response to the frequency band of themeshing of the gears 15 provided in the gear train 16.

A unit mounting portion 20 that includes a horizontally elongated upperattachment hole 17 and a lower attachment hole 18 provided below theupper attachment hole 17 is provided on the front portion of the mainbody frame 4. A drive unit 21 is mounted on the unit attachment portion20 (refer to FIG. 4).

As illustrated in FIG. 5 and FIG. 6, the drive unit 21 includes aplate-shaped attachment plate 22 as a frame member, a clutch 23 fixed toa lower portion of the inner surface of the attachment plate 22, and agear train 25 fixed with the clutch 23 to an inner surface of theattachment plate 22. FIG. 5 is a perspective view of the drive unit seenfrom an inner side of the main body 2, in which the right side of FIG. 5is the front side of the main body 2. In contrast, FIG. 6 is aperspective view of the drive unit 21 seen from an outer side of themain body 2, in which the left side of FIG. 6 is the front side of themain body 2.

The attachment plate 22 is formed by a sheet metal member, andconstitutes a portion of the gear box 26 that encloses the gear train25.

The perforated portion 28 that includes a plurality of holes 27 isformed along the whole region of the attachment plate 22. The gear train25 is disposed on an inner side of the perforated portion 28. The holeinterval and aperture diameter of the plurality of holes 27 in theperforated portion 28 (refer to the arrow b in FIG. 6) is set inresponse to the frequency band of meshing of the gear train 25.

The clutch 23 is inserted into the lower attachment hole 18 of the mainbody frame 4.

The gear train 25 is configured by a plurality of intermeshing gears 30.A portion of the gear train 25 is inserted into the upper attachmenthole 17 of the main body frame 4.

The peripheral edge portion 31 of the main body frame 4 is curvedoutwardly in a substantially orthogonal configuration in the main body2. A lower end engaging hole 32 is provided respectively in the frontportion, the rear portion and longitudinal central portion of the lowerend portion of the peripheral edge portion 31. An upper end engaginghole 33 is provided in the rear portion of the upper end portion of theperipheral edge portion 31 (refer to FIG. 3).

A resinous right cover 34 is provided on an outer side of the main bodyframe 4 as an external cover member that constitutes a portion of theexternal cover 3.

As illustrated in FIG. 7, the lower edge portion 35, the upper edgeportion 36 and the front edge portion 37 of the right cover 34 curvesinwardly (towards the main body 2, towards the main body frame 4) in asubstantially orthogonal configuration. A lower end hook 38 isrespectively provided on the lower end portion 35 at a positioncorresponding to the lower end engaging hole 32 of the main body frame4. An upper end hook 40 is provided on the upper end portion 36 at aposition corresponding to the upper end engaging hole 33 of the mainbody frame 4. The right cover 34 is configured to be assembled with themain body frame 4 by engaging the lower end hook 38 with the lower endengaging hole 32 and engaging the upper end hook 40 with the upper endengaging hole 33.

A rear rib 41 is formed on a lower rear portion of an inner surface ofthe right cover 34 to configure a first space forming portion 100 at aposition corresponding to the perforated portion 14 provided on thebulging portion 5 of the main body frame 4. The rear rib 41 projects toform an annular configuration that forms a horizontally long rectanglewhen viewed from the side. The “annular configuration” referred to abovemeans that the rear rib 41 is provided continuously so that a portion ofthe inner surface of the right cover 34 is partitioned from the otherportion, and there is no necessity for the formation of a circularshape.

As illustrated in FIG. 8, the rear rib 41 adjusts the height ofprojection from the inner surface of the right cover 34 to abut with theouter surface of the bulging portion 5 on an outer peripheral portion ofthe perforated portion 14 in a state in which the right cover 34 isassembled with the main body frame 4. In this manner, a substantiallyrectangular space 42 that is enclosed on an outer side is formed betweenthe right cover 34 and the perforated portion 14 of the main body frame4 by the rear rib 41, the outer surface of the perforated portion 14,and the inner surface of the right cover 34. The first space formingportion 100 forms a space between the perforated portion 14 and theright cover 34 that is tightly enclosed except for the perforatedportion 14. In the present embodiment, the first space forming portion100 is configured by the rear rib 41, the outer surface of theperforated portion 14 and the inner surface of the right cover 34. Theinterval between the inner surface of the right cover 34 and the outersurface of the perforated portion 14 in the space 42 (refer to the arrowX in FIG. 8) is set in response to the meshing frequency band of thegear train 16.

A front rib 43 configuring a second space forming portion 200 is formedon the front side of the inner surface of the right cover 34 from apredetermined upper position to a predetermined lower position. Thefront rib 43 projects to form an annular configuration. The “annularconfiguration” referred to above means that the front rib 43 is providedcontinuously so that a portion of the inner surface of the right cover34 is partitioned from the other portion, and there is no necessity forthe formation of a circular shape.

The front rib 43 is configured in a shape corresponding to the outeredge shape of the attachment plate 22, and the height of projection ofthe front rib 43 from the inner surface of the right cover 34 isadjusted so that the front rib 43 abuts with the attachment plate 22 onan outer peripheral portion of the perforated portion 28 in a state inwhich the right cover 34 is assembled with the main body frame 4. Inthis manner, as illustrated in FIG. 10, a flat space 44 that is enclosedon an outer side is formed between the right cover 34 and the perforatedportion 28 of the attachment plate 22 by the front rib 43, the outersurface of the perforated portion 28, and the inner surface of the rightcover 34. The second space forming portion 200 forms a space between theperforated portion 28 and the right cover 34 that is tightly enclosedexcept for the perforated portion 28. In the present embodiment, thesecond space forming portion 200 is configured by the front rib 43, theouter surface of the perforated portion 28 and the inner surface of theright cover 34. The interval between the inner surface of the rightcover 34 and the outer surface of the perforated portion 28 in the space44 (refer to the arrow Y in FIG. 10) is set in response to the meshingfrequency band of the gear train 25. In the present embodiment, theinterval between the perforated portion 28 and the right cover 34 in thespace 44 is narrower than the interval between the right cover 34 andthe perforated portion 14 in the space 42.

Although omitted from the figures, the inner portion of the monochromeprinter 1 is provided with a drum unit that houses photosensitive drums,a charging unit that applies a charge up to a predetermined voltage tothe surface of the photosensitive drums, an exposure unit that exposeslight onto the surface of the photosensitive drums that have beencharged by the charging device, a development unit that uses toner todevelop an electrostatic latent image formed by the exposure device intoa toner image, a transfer unit that operates cooperatively with thephotosensitive drums to execute transfer of the toner image onto thesurface of a transfer sheet, and a fixing unit that fixes the tonerimage that has been transferred onto the transfer sheet.

When the monochrome printer 1 that has the above configuration isoperated, the gear train 16, 25 is driven by the motor 12. At the sametime, each unit is driven and an image forming process is performed inthe monochrome printer 1.

On the other hand, when the gear train 16, 25 (sound generating source)is driven, each gear 15 in the gear train 16 and each gear 30 in thegear train 25 rotate. In this manner, a driving sound is generated.However, in the present embodiment, as described above, the gear train16, 25 is disposed at a position corresponding respectively to theperforated portion 14, 28 in an inner portion of the main body 2. Spaces42, 44 (the space enclosed with the exception of the perforated portions14, 28) that are enclosed on an outer side between the perforatedportion 14, 28 and the right cover 34 are respectively formed.

The sound that is generated by the gear train 16, 25 is screened andabsorbed when passing through the spaces 42, 44. In this manner, soundis reduced.

As a result, the monochrome printer 1 (image forming apparatus) enablesa reduction in sound emitted to the outside after passing through themain body frame 4, the attachment plate 22 and the right cover 34.

The space 42 is configured only by the main body frame 4 and the rightcover 34, and the space 44 is only configured by the attachment plate 22and the right cover 34. That is to say, the provision of the perforatedportion 14 directly to the existing main body frame 4 or the attachmentplate 22 means that the spaces 42, 44 can be formed without addition ofa new member provided with holes. Consequently, the monochrome printer 1(image forming apparatus) according to the present embodiment enablessound reduction as described above based on cost reduction andspace-efficient design.

Furthermore, the gear train 16 driven by a motor 12 mounted on a mainbody frame 4 is a sound generating source, and the monochrome printer 1(image forming apparatus) according to the present embodiment enables anintegrated configuration of the gear train 16 that is the soundgenerating source, the main body frame 4, and the motor 12. As a result,sound reduction and downsizing of the monochrome printer 1 are realizedsimultaneously.

An annular front rib 43 and rear rib 41 project on an inner surface ofthe right cover 34 in the monochrome printer 1 (image forming apparatus)according to the present embodiment. Furthermore the monochrome printer1 (image forming apparatus) forms spaces 42, 44 by the front rib 43 andthe rear rib 41, the outer surface of the perforated portion 14 and theinner surface of the right cover 34. In this manner, the monochromeprinter 1 (image forming apparatus) enables formation of the spaces 42,44 with a simple configuration.

The aperture diameter and the hole interval of the holes 13 provided inthe perforated portion 14 are set in response to the frequency band ofthe sound of the gear train 16 (the meshing frequency band of the geartrain 16), and the aperture diameter and the hole interval of the holes27 provided in the perforated portion 28 are set in response to thefrequency band of the sound of the gear train 25 (the meshing frequencyband of the gear train 25). As a result, the monochrome printer 1 (imageforming apparatus) ensures suppression of driving sound of a specificfrequency produced by the gear trains 16, 25.

Furthermore, the interval between the perforated portion 14 and theright cover 34 is set in response to the frequency band of the sound ofthe gear train 16 (the meshing frequency band of the gear train 16), andthe interval between the perforated portion 28 and the right cover 34 isset in response to the frequency band of the sound of the gear train 25(the meshing frequency band of the gear train 25). Consequently, themonochrome printer 1 (image forming apparatus) enables a furtherreduction in sound of a specific frequency generated by the soundgenerating source.

As described above in the present embodiment, the monochrome printer 1(image forming apparatus) is configured to enable setting of a frequencyband enabling sound reduction by a component design in which theinterval between the perforated portion 14, 28 and the right cover 34,and the aperture diameter and hole interval of the holes 13, 27 are setin response to the frequency band of the sound of the gear train 15, 25that is the sound generating source. The monochrome printer 1 (imageforming apparatus) combines a plurality of spaces 42, 44 respectivelyconfigured to set an interval between the perforated portion 14, 28 andthe right cover 34, and the aperture diameter and hole interval of theholes 13, 27 to thereby enable suppression of sound emission to theoutside by ensuring reduction in driving sound even when a driving soundis produced in a frequency band that is different from the plurality ofgear trains 16, 25.

The effect of the present invention was confirmed by an experimentperformed under actual conditions using a monochrome printer LS-4020DN(45 PPM) that is modified (60 PPM) and manufactured by Kyocera MitaCorporation.

In the experiment, a space 42 is formed between the right cover 34 andthe perforated portion 14 of the main body frame 4. In example 1 toexample 3, a sound frequency and sound pressure level for sound emittedto the outside from the monochrome printer was measured. The intervalbetween the main body frame 4 and the right cover 34, and the aperturediameter and hole interval of the holes 13 in the perforated portion 14in each example are respectively illustrated in FIG. 11. In acomparative example, a monochrome printer not provided with the mainbody frame 4 and the right cover 34 (comparative example 1) and amonochrome printer provided with the main body frame 4 and the rightcover 34 but without the perforated portion 14 in FIG. 4 (comparativeexample 2) were measured in the same manner as the examples.

In the experiment, the sound frequency that is the object for reductionwas 750 Hz. This frequency corresponds to the frequency of a meshingsound of large-bore gears and the motor pinion fixed to an output shaftof the motor 12. The raw data for sound on the right of the monochromeprinter is recorded, and the frequency and sound pressure level wereanalyzed using FFT analysis software (DS-0250 manufactured by Ono SokkiCo., Ltd.) and an FFT analyzer (DS-2000 manufactured by Ono Sokki Co.,Ltd.).

As clearly shown by the experimental results in FIG. 12 and FIG. 13, inall of example 1 to example 3, the sound pressure level is suppressedmore than comparative example 1 and comparative example 2 in the 630-800Hz frequency band that includes the 750 Hz that is the target frequencyto suppress(refer to the portion enclosed by the dotted line in FIG. 12and FIG. 13). Use of the configuration disclosed in the embodiments hasbeen verified to enable a reduction in sound of a specific frequency inan image forming apparatus.

As illustrated in FIG. 12 and FIG. 13, the sound pressure level in eachsound frequency is modified by varying the hole interval and aperturediameter of the holes 13 in the perforated portion 14. The presentembodiment has proved that component design enables determination of afrequency band that can be reduced (suppressed).

In the present embodiment, although the motor 12 was provided on anouter portion of the spaces 42, 44, in a different embodiment, the motor12 may be disposed in an inner portion of the spaces 42, 44. The imageforming apparatus enables reduction (suppression) of emission of therotational sound of the motor 12 to the outside, and further improvesreduction of sound emitted to the outside of the monochrome printer 1.

In the present embodiment, although a monochrome printer was describedas an image forming apparatus, there is no particular limitation in thisregard, and for example, the image forming apparatus may be a colorprinter, a monochrome or color copying machine, a facsimile, or amultifunction peripheral combining such devices.

1. An image forming apparatus comprising: a main body; a plate-shapedframe member configuring a part or the whole of the side surface of themain body; a perforated portion having a plurality of holes and formedin the frame member; a sound generating source in an inner portion ofthe main body and disposed at a position corresponding to the perforatedportion; an external cover member disposed at and separated by apredetermined distance from the frame member on an outer side of theframe member; and a space forming portion forming a space between theperforated portion and the external cover member, the space formingportion being tightly enclosed except for the perforated portion.
 2. Theimage forming apparatus according to claim 1, wherein the soundgenerating source is a gear train mounted on the frame member.
 3. Theimage forming apparatus according to claim 1, further comprising anannular rib projecting on an inner surface of the outer covering member,and the space forming portion configured by the rib, the outer surfaceof the perforated portion, and the inner surface of the outer coveringmember.
 4. The image forming apparatus according to claim 3, wherein theframe member comprises a bulging portion that projects on a main bodyinner portion, and the perforated portion is formed on the bulgingportion.
 5. The image forming apparatus according to claim 1, whereinthe plurality of holes that configure the perforated portion is formedwith an aperture diameter and a hole interval that are set in responseto the frequency band of the sound of the sound generating source. 6.The image forming apparatus according to claim 1, wherein the spaceforming portion sets the interval between the inner surface of the outercovering member and the outer surface of the perforated portion inresponse to the frequency band of the sound generated by the soundgenerating source.
 7. The image forming apparatus according to claim 1,wherein the sound generating source includes a motor that drives thegear train, and the motor is disposed in a space formed by the spaceforming portion.